The present invention relates to heat exchangers, and, more particularly, to the combination of two different fin surfaces to improve the thermal performance of a heat exchanger.
Heat exchangers are widely used for absorptive thermal protection. To achieve this, heat exchangers are made of various types of corrugated fin material to allow energy transfer during passage of air and fluid through the exchanger. However, a boundary layer of fluid thickness adheres to the heat exchanger or turbulizer, reducing the effectiveness of energy movement from one fluid to another, where a turbulizer is an enhancement made to the surface of the heat exchanger to effectively change the flow characteristic of the fluids.
The type of fin used for heat exchangers or turbulizers is usually dependent on a variety of factors. For example, lanced fin is used when volume available is at a premium. Lanced fin heat exchangers are compact and are capable of breaking up the boundary layer very well. However, one problem with using a lanced turbulizer is that the lanced turbulizer has a very short length before interruption, thereby increasing the pumping energy necessary to transfer a unit of energy.
Alternatively, ruffled fin may be used when volume of space is not the most critical consideration. Ruffled fin turbulizers can achieve the same thermal performance as lanced fin turbulizers, but with lower energy consumption per unit of energy transferred. However, a problem with using standard ruffled fin is that ruffled fin has a very long surface which builds thick fluid films, thereby decreasing its effectiveness to transfer heat.
It is seen then that there exists a need for a heat exchanger which has the short length effectiveness advantage of lanced fin, and the mixing advantage of ruffled fin, while overcoming the disadvantages of each.